The invention relates to solar energy collectors and particularly to the type of collector commonly referred to as a flat plate collector wherein a flat, heat absorbing plate is mounted in an insulated chamber and covered by a single or double panel of glass. Such conventional collectors generally are fairly expensive in that they commonly utilize copper panels to which copper tubing is attached, such as by brazing, as an absorbing surface. Such collectors are also of limited efficiency since significant energy is lost through the housing and glass due to conduction and re-radiation losses resulting from the large temperature differential that exists between the stationary absorber plate and the ambient. A further deficiency of conventional flat plate collectors relates to the problems caused by the use of water as a heat transfer fluid. The requirement for pumps is a significant expense while freezing and pipe expansion due to varying temperatures can cause damage to the piping system and portions of a building subjected to any leaks in the piping. Corrosion of the tubing can also be a problem which can shorten the life of a collector and produce damage while the collection of moisture on the glass covers can decrease the efficiency of energy collection.